EP0547470B1 - Positive displacement machine of the spiral principle - Google Patents

Description

Field of the Invention

The invention relates to a displacement machine for compressible media with a plurality of spiral-shaped conveying spaces arranged in a fixed housing and with a displacer assigned to the conveying spaces, which is held on a disk-shaped rotor which can be driven eccentrically relative to the housing in such a way that each of its points has one of the circumferential walls during operation the displacement chamber performs limited circular movement, for which purpose an eccentric disk is arranged on the drive shaft, on which the rotor is mounted by means of an oil-lubricated bearing.

State of the art

Displacement machines of the spiral type are known for example from DE-C-26 03 462. A compressor constructed according to this principle is characterized by an almost pulsation-free conveyance of the gaseous working medium, which consists, for example, of air or an air-fuel mixture, and could therefore also be used with advantage for charging purposes of internal combustion engines, among other things. During the operation of such a compressor are spiraled along the displacement chamber between the Trained displacement body and the two circumferential walls of the displacement chamber including several, approximately crescent-shaped work spaces that move from the inlet through the displacement chamber to the outlet, their volume constantly being reduced and the pressure of the working medium being increased accordingly.

A machine of the type mentioned at the outset is known from EP 0 354 342. In this machine and in all the other known scroll compressors, in which a guide shaft which is angularly synchronous with the drive shaft is provided for translatory guiding of the rotor, the drive shaft is mounted in roller bearings . This is particularly evident in the displacement machine according to EP 0 354 342, in which the drive shaft is mounted in the housing in two ball bearings and the eccentric collar arranged on the drive shaft is supported by a needle bearing.

This type of support or mounting of the rotor is relatively expensive, since for reasons of space a needle bearing without an inner race is used. However, this requires that the rolling path on the eccentric collar must be hardened, which in turn limits the selection for a cheap manufacturing method for the eccentric shaft. A convenient method is the casting process if nodular cast iron is used. Ductile iron is hardenable; However, the strength required for a heavily loaded rolling bearing operation is not achieved in the raceway, as is the case, for example, with rolling bearing steel.

Since, in addition, due to the high centrifugal force and the eccentric movement, permanent grease lubrication of the rolling bearing is eliminated, these known, highly loaded needle bearings are oil-lubricated, the oil being supplied to the bearing via a bore system in the drive shaft.

Presentation of the invention

Based on the knowledge that, as a result of the high thermal and mechanical loads on the main eccentric bearing, it is not possible to do without a continuous lubrication with a liquid lubricant, the object of the invention is to simplify the bearing concept of the displacement machine with regard to cost optimization.

The object is achieved in that a sliding bearing is provided for the orbiting rotor on the rotating eccentric disc, the oil supply and oil discharge being effected via a bore in the eccentric disc, and in that means for air-free oil supply in the sliding bearing gap are arranged within the eccentric disc.

Apart from the fact that the machine is cheaper because, in addition to replacing a rolling bearing with a plain bearing, its smaller radial dimensions also increase the free space required for the air flow, the particular advantage is that this measure results in a hardened surface of the Eccentric disc can be dispensed with. The indirect application of oil to the lubrication gap via degassing agent makes it possible to provide air-free oil for the highly loaded eccentric bearing in a simple manner
It is expedient if a cavity which is open towards the lubrication gap is arranged in the eccentric disc, specifically in the angular plane in which the eccentric disc is at its greatest distance from the axis of rotation. The oil supply is preferably carried out in the cavity via a bore in the eccentric disc, the mouth of which is arranged radially outside the axis of rotation of the drive shaft. The oil removal and, if necessary, the air removal takes place jointly via a longitudinal bore branching off the cavity and lying in the axis of rotation of the drive shaft. As a result of this measure, the oil flowing into the cavity is thrown into the lubricating gap as a result of the centrifugal force, while any air present in the oil is expelled by the action of this centrifuge and flows out of the cavity via the longitudinal bore. In addition, the cavity in the eccentric disc causes a reduction in the rotating mass; The drive shaft becomes lighter overall and less centrifugal force has to be compensated, which in turn leads to lighter compensating masses.

If a channel is arranged in the area of the radial plane of the lubrication gap, which extends in the circumferential direction of the lubrication gap from the cavity and against the direction of rotation of the drive shaft, a simple means is created to direct the air-free lubricating oil to the most heavily loaded point of the eccentric bearing.

In order to remove any air that may penetrate through the highly loaded shaft sealing rings on both sides of the plain bearing, it is appropriate to arrange a clear space on the circumference of the eccentric disc, which extends between the shaft sealing rings and which connects the oil spaces on both sides of the shaft sealing rings with the cavity. This clear space is preferably of a crescent shape, the center line of the sickle being like that of the cavity in the angular plane in which the eccentric disc is at its greatest distance from the axis of rotation (34),

Brief description of the drawing

In the drawing, an embodiment of the invention is shown schematically.

Fig. 1

einen Querschnitt durch das antriebsseitige Gehäuseteil der Verdrängermaschine nach Linie I-I in Fig. 2;

Fig. 2

einen Längsschnitt durch die Verdrängermaschine nach Linie II-II in Fig. 1;

Fig. 3

eine unbestückte Antriebswelle;

Fig. 4

einen Querschnitt durch die Antriebswelle nach Linie IV-IV in Fig. 3;

Fig. 5

einen Teilquerschnitt durch die Exzenterlagerung.

It shows:

Fig. 1

a cross section through the drive-side housing part of the displacement machine according to line II in Fig. 2;

Fig. 2

a longitudinal section through the displacement machine according to line II-II in Fig. 1;

Fig. 3

a bare drive shaft;

Fig. 4

a cross section through the drive shaft according to line IV-IV in Fig. 3;

Fig. 5

a partial cross section through the eccentric bearing.

Way of carrying out the invention

In order to explain the operation of the compressor, which is not the subject of the invention, reference is made to the already mentioned DE-C3-2 603 462. In the following, only the machine structure and process flow necessary for understanding are briefly described.

In Fig. 1, the housing with the delivery rooms and the inserted displacer is shown. The rotor of the machine is designated as a whole by 1. On both sides of the disc 2, two spiral-shaped displacers are arranged, which are offset by 180 ° to one another. These are strips 3a, 3b which are held vertically on the pane 2. In the example shown, the spirals themselves are formed from a plurality of circular arcs adjoining one another. 4 denotes the hub with which the disk 2 over the slide bearing 22nd is mounted on an eccentric disk 23. This eccentric disk is in turn part of the drive shaft 24.

5 with a radially outside the strips 3a, 3b arranged eye is designated for receiving a guide bearing 25 which is mounted on an eccentric bolt 26. This is in turn part of a guide shaft 27. At the spiral end, four passage windows 6, 6 'are provided in the disk so that the medium can get from one disk side to the other, for example to be drawn off in a central outlet arranged only on one side.

1 shows the housing half 7a shown on the left in FIG. 2 of the machine housing which is composed of two halves 7a, 7b and is connected to one another via fastening eyes 8 for receiving screw connections. 11a and 11b denote the two delivery spaces, each offset by 180 °, which are worked into the two housing halves in the manner of a spiral slot. They each run from an inlet 12a, 12b arranged on the outer circumference of the spiral in the housing to an outlet 13 provided in the interior of the housing and common to both delivery spaces (FIG. 2). They have essentially parallel, uniformly spaced cylinder walls 14a, 14b, 15a, 15b, which in the present case, like the displacer bodies of the disk 2, comprise a spiral of approximately 360 °. The displacers 3a, 3b engage between these cylinder walls, the curvature of which is dimensioned such that the strips almost touch the inner and outer cylinder walls of the housing at several, for example at two points each. On the free end faces of the strips 3a, 3b and the webs 45, 46, seals 49 are inserted in corresponding grooves. With them, the working rooms against the side walls of the housing respectively. sealed against the displacement disc.

The drive and the guide of the rotor 1 are provided by the two spaced-apart eccentric arrangements 23, 24 and. 26, 27. The drive shaft 24 is mounted on the drive side in a roller bearing 17 and on the air side in a slide bearing 18. At its end protruding from the housing half 7a, it is provided with a V-belt pulley 19 for the drive. Counterweights 20 are arranged on the drive shaft 24 to compensate for the inertial forces arising when the rotor is eccentrically driven. The guide shaft 27 is inserted within the housing half 7a in a slide bearing 28, which is sealed on both sides with ring seals 39. In order to achieve clear guidance of the rotor in the dead center positions, the two eccentric arrangements are synchronized with a precise angle via a toothed belt drive 16. This double eccentric drive ensures that all points of the rotor disc and thus also all points of the two strips 3a and 3b perform a circular displacement movement. As a result of the multiple alternating approaches of the strips 3a, 3b to the inner and outer cylinder walls of the associated delivery chambers, crescent-shaped workrooms enclosing the working medium result on both sides of the strips, which are displaced by the delivery chambers in the direction of the outlet during the drive of the rotor disk. The volumes of these working spaces decrease and the pressure of the working fluid is increased accordingly.

A common system is provided for lubricating the bearings accommodated in the housing 7a, 7b and the main eccentric bearing 22. Lubricant, preferably oil, is passed from a lubricant source (not shown) to the slide bearing 28 via a bore 29 in the housing half 7b. The oil is collected on both sides of this bearing and guided through a bore 30 into the area of the drive shaft 24 between the roller bearing 17 and the associated drive-side shaft sealing ring 50. From there, the oil penetrates and lubricates the roller bearing 17 and reaches an annular space 51, which is laterally closed by another shaft sealing ring 52.

The eccentric bearing 22 is now fed from this annular space 51. This bearing is designed as a simple slide bearing and is sealed against the interior of the machine via shaft sealing rings 32, as can be seen in FIG.

A direct oil supply via radial bores in the eccentric disk to the two bearing sides, as is known, for example, from EP 0 354 342 mentioned at the outset, would be disadvantageous in the present case. On the one hand, air already contained in the oil would impair its lubricity; on the other hand, additional air can flow into the storage space via the shaft sealing rings provided on both sides of the bearing. This is because the interior of the machine - in which the eccentric drive is located - beyond the shaft seals is under pressure during operation.

As can be seen from FIGS. 2 to 5, the lubricant is accordingly fed into the lubrication gap in the middle of the bearing. This is done via a straight oblique bore 31 in the eccentric disc. The oblique bore communicates on the drive side with the annular space 51 and opens into a cavity 33 within the disk. The cavity is open to the lubrication gap. The opening of the cavity extends over a circumferential area X (FIG. 1) and is located in the angular plane in which the eccentric disc has its largest radial dimension. The mouth of the oblique bore 31 is arranged in a radial plane which is located outside the axis of rotation 34 of the drive shaft. On the occasion of the rotation, the oil flowing into the cavity is thrown outward into the peripheral region X due to centrifugal force. If there is air in the oil, it is separated from the oil under the action of the centrifuge. This air flows radially inwards into the center of rotation of the cavity, which coincides with the axis of rotation 34 of the drive shaft coincides. The air and the oil not required for lubrication are then discharged from the cavity 33 via a longitudinal bore 53 arranged centrally in the drive shaft.

Now, of course, precautions are also to be taken against air entering laterally through the shaft sealing rings 32. For this purpose, the eccentric disk is pierced in the area of the shaft sealing rings in order to form a crescent-shaped space 35 (FIG. 4). This space is located in the same angular plane as the circumferential area X and extends axially between the two shaft sealing rings 32. It connects the oil spaces 58 arranged on both sides of the shaft sealing rings to the cavity 33. This space 35 is produced in a simple manner by the eccentric disk is ground at the corresponding point from the axis of rotation as the center with the radius of the eccentric disc. As can be seen from FIG. 5, air which penetrates the highly loaded shaft sealing rings 32 orbiting with the eccentricity passes directly from the oil spaces 58 into this space 35 bypassing the lubrication gap and then flows radially inwards along the wall of the cavity 33 its center of rotation.

In the peripheral area X there is thus virtually air-free oil, which acts on the lubricating gap of the plain bearing. It is now important to bring the oil to those bearing points that are most heavily contaminated.

In Fig. 1, the reaction force of the eccentric disc caused by the centrifugal force is designated F. The reaction force caused by the drive of the rotor is labeled A. The resulting reaction force is shown with the arrow R. This resultant causes the highest load in the Y bearing area. In relation to the eccentric disc, this area Y is always in the same place.

At most, shifts up or down occur due to a varying drive power or centrifugal force.

With free oil flow in an eccentric disc, the oil tends to be thrown into area X due to the centrifugal force field. This is independent of the new measure of the cavity arrangement. Since the lubricant flows in the lubrication gap counter to the direction of rotation in the case of eccentric bearings, there could be a risk that the oil will not adequately supply area Y due to the long distance to be covered. Experiments have now shown that there is sufficient oil supply in the heavily loaded area Y when the oil is fed into the area designated Z in FIG. 1. Relative to the center of rotation and seen in the direction of rotation, this area Z lies approximately 90 ° in front of the most heavily loaded area Y.

In order to ensure this oil supply, a recess is formed on the outer circumference of the eccentric disk, which forms a channel 40 connecting the cavity 33 and the region Z. As can be seen in FIG. 4, this channel runs counter to the direction of rotation of the drive shaft. The air-free oil thus freshly fed into the peripheral area Z from the peripheral area X easily retains its load-bearing capacity and lubricity right up to the endangered peripheral area Y. In order to better illustrate the channel 40, the drive shaft 24 is shown in FIG rotated by 180 ° in Fig. 2, d. H. the drive side is in the right part of the figure. The balancing weight 20 shown hatched in FIG. 2 is also not attached to the shaft shown in FIG. 3 in the preassembled state.

The oil flowing out of the longitudinal bore 53 on the air-side end face of the drive shaft still has the task of lubricating the less loaded air-side shaft bearing 18.

This bearing is designed as a plain bearing and is provided on both sides with oil spaces 54, 55, which are sealed off from the outside. For this purpose, the oil space 55 on the drive side is delimited by a shaft sealing ring 56 acting against the drive shaft. The opposite oil chamber 54, in which the longitudinal bore 53 opens, is closed by the wall of the housing part 7a. The two oil spaces 54, 55 are connected to one another via a channel 57. For this purpose, this channel is designed as a depression in the bearing 18. The channel is open towards the drive shaft 24 along its entire axial length, as a result of which the bearing 18 is fed uniformly.

Claims (8)

1. Displacement machine for compressible media, having a plurality of spiral-shaped delivery chambers (11a, 11b) disposed in a fixed housing (7a, 7b) and having a displacement body (1-4) assigned to the delivery chambers, which displacement body is held in such a way on a disc-shaped rotor (1), which can be driven eccentrically relative to the housing, that, during running, each of its points performs a circular motion limited by the peripheral walls of the delivery chambers, for which purpose there is disposed on the drive shaft (24) an eccentric disc (23) on which the rotor (1) is mounted by means of an oil-lubricated mounting, characterized in that, for the orbiting rotor (1), a slide bearing (22) is provided on the rotating eccentric disc (23), the supply of oil and evacuation of oil being effected via a bore (31 and 53 respectively) in the eccentric disc, and in that within the eccentric disc there are disposed means for the air-free supply of oil into the slide bearing gap.
2. Displacement machine according to Claim 1, characterized in that the means for the air-free supply of oil into the slide bearing gap essentially comprise a cavity (33), which is disposed in the eccentric disc (24) and is open towards the lubricating gap, to be precise in the angular plane in which the eccentric disc exhibits its greatest distance to the rotational axis (34), the supply of oil being effected into the cavity (33) and the evacuation of oil and, where appropriate, the evacuation of air being jointly effected via a longitudinal bore (53) which branches off from the cavity (33) and lies in the rotational axis (34) of the drive shaft (24).
3. Displacement machine according to Claim 2, characterized in that the mouth of the oil-supplying bore (31) into the cavity (33) is disposed radially outside the rotational axis (34) of the drive shaft (24), and in that the mouth of the oil-evacuating bore (53) from the cavity (33) is disposed in the rotational axis (34) of the drive shaft (24).
4. Displacement machine according to Claim 2, characterized in that on the periphery of the eccentric disc (23) there is provided a clear space (35), which extends between the rotary shaft seals (32) disposed on both sides of the bearing (18) and which connects the oil chambers (58) on both sides of the rotary shaft seals (32) to the cavity (33).
5. Displacement machine according to Claim 4, characterized in that the clear space (35) is crescent-shaped, and in that the centre line of the crescent is located in the angular plane in which the eccentric disc exhibits its greatest distance to the rotational axis (34).
6. Displacement machine according to Claim 2, characterized in that in the region of the radial plane of the lubricating gap a duct (40) is disposed, which duct extends from the cavity (33) in the peripheral direction of the lubricating gap, to be precise, counter to the direction of rotation of the drive shaft (24).
7. Displacement machine according to Claim 6, characterized in that the duct (40) is configured as a recess on the outer periphery of the eccentric disc (23).
8. Displacement machine according to Claim 2, characterized in that the oil flowing from the longitudinal bore (53) on the air-side end face of the drive shaft (24) is guided into a shaft bearing (18) configured as a slide bearing, which bearing is closed off at its two axial ends by oil chambers (54, 55), and in that the two oil chambers (54, 55) communicate with each other via a duct (57), the duct being open, in its axial extent, towards the drive shaft (24).

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